1. Field of the Invention
The invention relates to a record carrier comprising a servo track indicating an information track intended for recording information blocks represented by marks having lengths expressed in channel bits, this servo track having a wobble being a periodic variation of a physical parameter, and the servo track constituting a concentric or spiral pattern of substantially parallel tracks at a track pitch t.
The invention further relates to recording and/or playback device comprising means for writing and/or reading information blocks represented by marks having lengths expressed in channel bits in an information track on the record carrier, which device comprises means for scanning the servo track and retrieving the record carrier information.
The invention further relates to a method for manufacturing the record carrier.
2. Description of the Related Art
A record carrier and device of the type defined in the opening paragraph, for reading and/or writing information, are known from International Patent Application No. WO 00/43996, corresponding to U.S. Pat. Nos. 6,538,982 and 6,765,861. The information is encoded into an information signal which includes time codes and may be subdivided in accordance with these time codes into information blocks, the time codes being used as addresses, such as, with CD-ROM or DVD+RW. The record carrier has a servo track, usually called pre-groove, for causing servo signals to be generated when scanning the track. A physical parameter, e.g., the radial position, of the pre-groove periodically varies constituting a so-called wobble. During the scanning of the track, this wobble leads to a variation of the servo signals and a wobble signal can be generated.
A problem of the known system is that the wobble signal is disturbed by cross-talk. This problem become increasingly important in newer optical recording systems, such as, DVD and DVR, because the tracks are closer together in these higher density systems (even when scaling with the optical parameter is taken into account), and thus, the cross-talk between tracks increases.